The present invention relates generally to a wave rotor apparatus and a method of using the transient gas dynamic processes within the wave rotor to accomplish an engine topping cycle. More particularly, in one embodiment of the present invention a portion of the gases in the highest pressure portion of the wave rotor based topping cycle are routed to a port adjacent to and preceding an inlet port admitting air from the compressor. Although the present invention was developed for use with a gas turbine engine, certain applications may be outside of this field.
A wave rotor is generally thought of as a generic term and describes a class of machines utilizing transient internal fluid flow to efficiently accomplish a desired flow process. Since the 1940""s wave rotors have been studied by engineers and designers, and identified as particularly adapted for use in a gas turbine engine. Performance levels of gas turbine engines are enhanced by the integration of a wave rotor based topping cycle thereon.
Presently, a considerable amount of research is directed to improving the specific power and decreasing the specific fuel consumption of gas turbine engines. One approach to obtaining these goals is to raise the compressor pressure ratio (compressor exit pressure/compressor inlet pressure), and/or increase the combustor temperature. However, several constraints have inhibited the realization of an aircraft gas turbine engine having a significantly raised compressor pressure ratios and/or combustor temperatures.
Increasing the pressure ratio causes an increased gas density that often necessitates the use of smaller passages and blading. Associated with smaller passages and blading is an increased surface area that can cause decreased component efficiency related to frictional losses. Also associated with smaller passages and blading are losses related to increased blade tip leakages due to proportionately larger tip clearances. Therefore, all or a portion of the theoretical improvement and cycle efficiency attributed to the increase in the pressure ratio may be negated by the decrease in component efficiency. Current material limitations and cooling techniques for aircraft gas turbine engines have been inadequate to accommodate significantly increased operating temperatures, thus, inhibiting any significant working fluid temperature increase in the gas turbine.
Suitably designed wave rotors can function like key portions to conventional gas turbine engines to extract useful work by compressing and expanding the working fluid. However, unlike the conventional gas turbine engine that utilizes rotating airfoils, the transfer and extraction of energy in a wave rotor involves unsteady transient waves and flow processes. The wave rotor used in a cycle topping role allows an increase in the engine pressure ratio without suffering high losses. Simultaneously, the combustor exit temperature can be increased while using present material technology because the wave rotor has a self cooling feature occurring within it""s passageways. The self cooling feature utilizes intermittently exposing individual passageway walls of the wave rotor to alternating elevated and reduced temperature gas flows, so that the thermal capacitance of the passageway walls can hold the average material temperature to an acceptable level.
Although prior wave rotors and methods of using transient gas flows are steps in the right direction, the need for additional improvements still remains. The present invention satisfied this need in a novel and unobvious way.
One embodiment of the present invention contemplates a combination of a gas turbine engine having a compressor and a turbine and a waver rotor comprising: a rotor having a plurality of passageways therethrough for gas flow; a plurality of sequential exit ports disposed in fluid communication with the rotor for receiving gas exiting the plurality of passageways, one of the plurality of exit ports being a first exit port having a pressure greater than the rest of the plurality of exit ports; a plurality of sequential inlet ports disposed in fluid communication with the rotor for allowing gas to flow into the plurality of passageways, one of the plurality of inlet ports being a compressor inlet port for receiving gas from the compressor; and a passageway coupled between the first exit port and a second of the plurality of inlet ports positioned adjacent to and prior the compressor inlet port for delivering gas to the rotor.
Another embodiment of the present invention contemplates a method utilizing a wave rotor to top a gas turbine engine""s cycle. The method comprising: providing the wave rotor having a rotatable rotor with a plurality of fluid passageways for the passage of a working fluid therethrough; rotating the rotor so as to sequentially pass the plurality of fluid passageways by a plurality of wave rotor inlet ports and a plurality of wave rotor outlet ports; discharging a portion of the working fluid within at least one of the plurality of fluid passageways through one of the plurality of outlet ports, wherein the one outlet port having the highest pressure of any of the plurality of outlet ports; reducing the pressure of the portion of the working fluid after the discharging; and introducing the portion of the working fluid into one of the plurality of inlet ports after the reducing.
One object of one form of the present invention is to provide an improved wave rotor for a gas turbine engine.
Related objects and advantages of the present invention will be apparent from the following description.